Problem: Ben starts counting at 20, and he counts by fours. If 20 is the 1st number that Ben counts. what is the 11th number that he counts?
Explanation: What is the first number that he counts? $20$ What is the second number that he counts? $\begin{align*}&20 + 4 \\ &= 24\end{align*}$ What is the third number that he counts? $\begin{align*}&20 + 4 + 4 \\ &= 20 + (2 \times 4) \\ &= 28\end{align*}$ What is the 11th number that he counts? $\begin{align*}&20 + (10\times4) \\ &= 20 + 40 \\ &= 60\end{align*}$